Physiological Monitoring-Based Implantable Drug Infusion System

ABSTRACT

A system and method for physiological monitoring and regulation of a drug infusion device. The system includes an internal compact unit that is implantable in a patient having a pulmonary disorder, the internal unit encasing a power supply, a fluid reservoir, a motor pump, a digital control unit, and a radio frequency transmitter. An infusion catheter is connected to the fluid reservoir and motor pump for automatically infusing a drug into a right ventricle of the patient during a diastole phase of a cardiac cycle. The system includes an external unit for monitoring and storing a plurality of physiological parameters of the patient and for making adjustments to a drug infusion rate.

TECHNICAL FIELD

Embodiments of the invention generally relate to medical devices and,more specifically, to implantable drug infusion systems associated withphysiological monitoring systems.

BACKGROUND

In the field of medical science, pulmonary arterial hypertension (PAH)is a heart/lung disorder in which the blood pressure in the pulmonaryarteries and/or pulmonary arterioles far exceeds normal levels. Theprecise causes of PAH are still not completely known. PAH manifests inthe form of shortness of breath, dizziness, fainting, and othersymptoms, all of which are exacerbated by physical exertion and stress.Pulmonary hypertension can be a severe disease with a markedly decreasedexercise tolerance and can result in heart failure, and eventuallydeath, for some patients.

The electrocardiogram (ECG or EKG) complex is defined by a plurality ofwaves, segments, and intervals as follows. The P-wave is the firstcomponent of the ECG complex and corresponds to atrial depolarization(contraction). It is usually a positive deflection from the baseline.The QRS complex corresponds with ventricular depolarization(contraction) and is measured from the beginning of the Q-wave or R-wave(if no Q-wave is present) to the end of the S-wave. The normal durationof the QRS complex is 0.04-0.11 seconds. The Q-wave is the firstnegative deflection of the QRS complex. The R-wave is the first positivedeflection of the complex. The S-wave is the negative deflectionfollowing the R-wave. Not every QRS complex has a Q, R, and S-wave. TheT-wave corresponds with ventricular repolarization (relaxation). TheU-wave is a small wave of low voltage and, if present, follows theT-wave. The PR segment begins at the end of the P-wave and continuesuntil the beginning of the QRS complex. The PR interval includes theP-wave and PR segment. The normal PR interval measurement is 0.12-0.20seconds. The ST segment is measured from the end of the QRS complex tothe beginning of the T-wave. The QT interval corresponds withventricular depolarization (contraction) and repolarization(relaxation). The normal QT interval measurement is 0.32-0.40 seconds.

SUMMARY

The disclosed embodiments relate to medical devices corresponding tophysiologically or pathophysiologically regulated or regulatable druginfusion. According to one embodiment, the disclosure pertains tomedical devices and methods associated with intrapulmonary arterial drugdelivery to patients suffering from pulmonary arterial hypertension,wherein the disclosed device is based on an implantable drug infusionassembly that has the ability to deliver drugs by physiological,automatic or external means, and yet does not compromise the healthsafety issues of pulmonary patients who receive such drug dosages.

In one embodiment, a system is provided for physiological monitoring andregulation of a drug infusion device. The system includes an internalcompact unit that is implantable in a patient having a pulmonarydisorder, the internal unit encasing a power supply, a fluid reservoir,a motor pump, a digital control unit, and a radio frequency transmitter.An infusion catheter is connected to the fluid reservoir and motor pumpfor automatically infusing a drug into a right ventricle of the patientduring a diastole phase of a cardiac cycle. The system includes anexternal unit for monitoring and storing a plurality of physiologicalparameters of the patient and for making adjustments to a drug infusionrate.

In one embodiment, an infusion catheter is provided for delivery of adrug into a patient having a pulmonary disorder. The infusion catheterincludes a radially dense helical structure made of a polyurethanematerial and having a supporting steel frame. A hemodynamic pressuresensor is mounted on a tip of the catheter for measuring a relativechange in hemodynamic pressure over time. A biopotential sensorincluding a biopotential sensing electrode is mounted on a tip of thecatheter for sensing an electrocardiogram signal of the patient. Theinfusion catheter is connected by a valve to a fluid reservoir and amotor pump in an implantable device and automatically infuses a druginto a right ventricle of the patient during a diastole (relaxation)phase of a cardiac cycle at a rate dependent on the measured change inhemodynamic pressure.

In one embodiment, a method is provided for hemodynamic monitoring of apatient diagnosed with pulmonary hypertension and infusion of atherapeutic drug by an implantable drug infusion device. The methodincludes monitoring the relative change in hemodynamic pressure in apatient's right ventricle over time by a pressure sensor mounted on atip of an infusion catheter in the implantable device; sensing anelectrocardiogram signal of the patient by a biopotential sensorincluding a biopotential sensing electrode mounted on a tip of theinfusion catheter; and infusing the therapeutic drug into the rightventricle during a diastole phase of a cardiac cycle at a rate dependenton the monitored relative change in hemodynamic pressure. The drug ispumped from a fluid reservoir in the implantable device through theinfusion catheter into the patient's right ventricle through an infusionport.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and aspects of the embodiments of thedisclosure will become apparent and more readily appreciated from thefollowing detailed description of the embodiments taken in conjunctionwith the accompanying drawings, as follows.

FIG. 1 illustrates an implantable drug infusion system in accordancewith an exemplary embodiment.

FIG. 2 illustrates a magnified view of an infusion catheter inaccordance with an exemplary embodiment.

FIG. 3 illustrates an exemplary schematic representation of rate ofpressure change in the right ventricle.

DETAILED DESCRIPTION

The following detailed description is provided as an enabling teachingof embodiments of the invention. Those skilled in the relevant art willrecognize that many changes can be made to the embodiments described,while still obtaining the beneficial results. It will also be apparentthat some of the desired benefits of the embodiments described can beobtained by selecting some of the features of the embodiments withoututilizing other features. Accordingly, those who work in the art willrecognize that many modifications and adaptations to the embodimentsdescribed are possible and may even be desirable in certaincircumstances. Thus, the following description is provided asillustrative of the principles of the invention and not in limitationthereof, since the scope of the invention is defined by the claims.

According to one embodiment, the implantable drug infusion systemprovides pulmonary arterial delivery of drugs to patients with pulmonaryarterial hypertension. Infusion systems have been used in drug deliveryprior to the present disclosure. However, prior systems have notprovided the capability of delivering drugs based on sensing andanalyzing cyclic hemodynamic, electrical occurrences within the heart.The infusate may be a vasodilatory agent or may serve the purpose ofdelivering gene therapy.

In one embodiment, the design of the drug infusion catheter includes aunique design to ensure forward-only phasic flow, thereby minimizing therisk of catheter malfunction, and therefore providing maximum patientsafety. Furthermore, using a drug infusion system, as described herein,for delivering drugs to pulmonary hypertension patients is also a uniqueconcept.

An embodiment of the implantable drug infusion system is illustrated inFIG. 1. The disclosed system includes both an external unit and aninternal unit. The internal unit resembles a pacemaker in design, and istypically implanted inside a pocket positioned under the collar bone andconnected to the heart using an infusion catheter. The components of theinternal unit include: power supply 1, fluid reservoir and motor pump 2,infusion catheter 3, pressure sensor 4, biopotential (ECG) sensor 5,digital control unit 6, and RF transmitter 7.

The external unit components are those components that are locatedoutside the patient's body, and such external components are generallyrelated to aspects of monitoring and storing of various physiologicalparameters and to making external adjustments to the drug flow rate.Examples of various physiological parameters include, but are notlimited to, heart rate, EKG, and right ventricle pressure. In oneexemplary embodiment, the components of the external unit includeadaptive RF powering system 8, RF receiver 9, and an adjustmentcomponent 10.

It will be understood that the power supply 1, fluid reservoir and motorpump 2, digital control unit 6, and RF transmitter 7 of the internalunit of the implantable drug infusion system are typically encased in aseparate unit herein referred to as the internal compact unit. Usually,the internal compact unit is circular or elliptical in shape, so as toavoid the presence of sharp corners that might damage internal tissuesor penetrate a patient's skin. In one embodiment, dimensions of theinternal compact unit of the drug infusion system are such that thevolume of the internal compact unit is between 6-8 cubic centimeters. Aswill be understood and appreciated by one of ordinary skill in the art,standard pacemaker pulse generators are typically sized similar to, orsomewhat smaller than, the internal compact unit of the disclosed druginfusion system. However, various embodiments of the drug infusionsystem could include different shapes and sizes as will occur to one ofordinary skill in the art, and are not limited to the specificdimensions or shapes described herein. Although in the exemplaryembodiments described herein, the drug infusion system includes tencomponents, no limitation of the scope of the disclosure is intendedthereby; any alterations and further modifications of the described orillustrated embodiments, and any further applications of the principlesof the disclosure are contemplated as would normally occur to oneskilled in the art to which the disclosure relates. For example, thenumber of components comprising the drug infusion system can involvegreater than or, alternatively, fewer than ten components.

For the purpose of promoting an understanding of the principles of thedisclosure, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Inother words, the various components illustrated in FIG. 1 that includethe internal and external units of the drug infusion system will bedescribed in greater detail.

Power Supply

For operation of the electrical circuitry within the internal compactunit of the disclosed implantable drug infusion system, a power supply 1is provided. In one embodiment, the power supply may include a lithiumbattery (for example, using lithium magnesium dioxide, or lithiumiodine, or lithium carbon monofluoride). Such lithium batteriestypically have long lives, slow discharge rates, and are suitable formemory backup. As will be understood, the life of such batteries isusually estimated through monitoring of internal resistance similar tocurrent pacemaker systems. However, since the implantable drug infusionsystem is expected to stay implanted inside a patient's heart for aduration shorter than that of pacemakers, complicated methods ofestimation of the life of the battery are generally not required. In oneembodiment, the dimensions of the power supply component of thedisclosed drug infusion system are 20 millimeters×20 millimeters×2millimeters.

Fluid Reservoir and Infusion Pump

According to one embodiment, the disclosed drug infusion system utilizesa fluid reservoir connected to an infusion pump for storage anddistribution of the given drug based on the cardiac cycle of a patient'sheart. As seen in FIG. 1, the fluid reservoir and infusion pumpcomponent is labeled with reference number 2. The fluid reservoir isessentially a subcutaneous reservoir that stores the drug. The fluidreservoir is filled periodically, or as needed, by making a perforationon the patient's skin using a needle. As will be understood by one ofordinary skill, the reservoir chamber that stores the drug is keptseparate from the motor pump chamber which pumps the drug out from thereservoir chamber into the patient's body. The motor pump chamber 2 isconnected to the power supply 1. Generally, the drug that will beadministered to a patient is in constant flow from the reservoir chamberto the pump chamber 2. The rate of flow of the drug from the pumpchamber 2 to the infusion catheter 3 is regulated by the output frompower supply 1 to the chamber 2, as shown in FIG. 1. It will beunderstood that the rate of flow from the pump chamber 2 to the infusioncatheter 3 ceases during systole (contraction), ensuring that the powersupply operated pump creates a peristaltic flow during a mechanicallyless active diastolic (relaxation) phase of a cardiac cycle. In oneembodiment, the rate of flow of the drug can be adjusted manually by aclinician.

Infusion Catheter

An infusion catheter 3 is connected via a valve to a fluid reservoir andmotor pump 2. As will be understood by one of skill in the art, theinfusion catheter 3 forms the conduit for drug delivery to the patient.A magnified view of an embodiment of the infusion catheter 3 is shown inFIG. 2. According to one aspect, the infusion catheter 3 is made ofpolyurethane with the supporting steel frame designed to provide radialstrength and reservoir-like functionality to the proximal portion. Asshown in FIG. 2, the proximal portion of the infusion catheter 3includes a radially dense helical structure that proximally functions asa fluid reservoir when there is no peristaltic flow created by the motorpump 2 during systole. It will be understood that the helical structureis designed in such a manner that it is resistant to collapse in theproximal portion during systole when 40 mm to 100 mm Hg pressure isgenerated. In the mid and distal portions of the catheter 3, the steelframe is more longitudinally oriented, increasingly parallel to the longaxis of the catheter 3, and becomes progressively less dense. As will beunderstood and appreciated, the distal collapse of the catheter 3prevents blood entrapment that could lead to clot formation. Thereservoir functionality provided by the proximal part of the catheter 3helps in flushing any residual blood within the more distal parts asperistaltic flow begins with a next cycle. From the foregoing, it willbe appreciated that the novel infusion catheter 3 allows unidirectional(i.e., forward) flow of the drug only during certain phases of thepatient's cardiac cycle, i.e., during diastole. The interior of thedistal portions of the catheter 3 (having exemplary dimensions of about2 cm to 3 cm, although other dimensions are possible) is coated withheparin or other thrombin inhibitors to prevent clotting.

Generally, the infusion catheter 3 contains pressure and EKG sensors 4located at its tip, and an infusion hole 1 cm away from the tip. Asshown in FIG. 1, a screw attached at the end of the infusion catheterallows the catheter to be anchored to the right ventricle wall in thepatient's heart, similarly to a pacemaker.

Pressure Sensor

As seen in FIG. 1, a hemodynamic pressure sensor 4 monitors the relativechange in right ventricle pressure change over time. For example, therate of change of ventricle pressure can be expressed mathematically asdp/dt wherein dp=pressure change, dt=time interval of change. As shownin FIG. 3, a typical dp/dt (vertical axis) versus time (horizontal axis)curve contains sharp deflections very relevant to the performance of theright ventricle which is closely related to pulmonary arterialpressures. As illustrated in FIG. 3, there are two positive deflectionsobserved in this curve.

One early positive deflection from the base of the curve to the point atwhich dp/dt is maximum occurs during isometric contraction of theventricle, whereas a late upward deflection from the point at whichdp/dt is minimum to the base occurs during isovolumetric relaxation.Analogous to the Tei index (myocardial performance index) or mechanicalperformance index determined by ultrasonography, the time duration ofthe sum of these two upward deflections normally should not exceed20%-25% of the time duration of a complete cardiac cycle.

As will be appreciated, aspects of this disclosure allow the infusionrate to be adjusted automatically or manually by external procedures.For example, an algorithm (method) can be used for the automaticadjustment of the infusion rate. It will occur to one of ordinary skillthat this technique of measuring relative changes in ventricle pressurehas several advantages over measurement of absolute pressures.

One advantage is avoiding intrinsic difficulties, including the need forperiodic calibration, associated with absolute pressure measurement.Another advantage is that the relative changes in ventricle pressure(typically measured in increments in pressure dp at dt intervals) can beconverted into digital values, and expressed as an output comprisingzeroes and ones. For example, positive increments in dp are expressed asan output one (‘1’), as indicated in FIG. 3. On the other hand, zero ornegative increments in dp are expressed as an output zero (‘0’). Withinone cardiac cycle, the ratio of the duration of sharp positivedeflections (output one) to the time duration of a complete cardiaccycle is an indicator of right ventricular condition. Normally thisratio lies in the range 0.2-0.4. The infusion rate can be increasedautomatically if the ratio exceeds 0.4. The ratio of output one (‘1’)versus output zero (‘0’) is closely related to the condition of theright ventricle, and moreover, the lower this ratio, the better is thecondition of the right ventricle. It will occur to one of ordinary skillthat even in normal individuals, pulmonary artery pressures may elevatewith exercise occasionally. Thus, it will be appreciated that it makesmore sense to track right ventricle performance in a relative sense, asopposed to attempting absolute pulmonary arterial pressure measurements.Moreover, it will be known by one skilled in the art that performance ofthe right ventricle is more closely related to the prognosis, and thusseveral aspects of the disclosure present in various beneficial ways.

As shown in FIG. 1, a pressure sensor 4 is connected to a digitalcontrol unit 6 which will be further described below. In one example ofthe disclosed system, details of an exemplary system architectureinvolving pressure sensors, and various other issues relating togathering and analyzing data collected by such sensors (including thedigital control unit 6 as shown in FIG. 1) are discussed in thefollowing technical publication: “Ubiquitous Monitoring Environment forWearable and Implantable Sensors (UbiMon),” by Jason W. P. Ng, Benny P.L. Lo et al., which is incorporated by reference herein. Accordingly,these details are not described herein.

Biopotential (ECG Sensor) Sensing Electrodes

In one embodiment, the electrocardiogram (EKG or ECG) signal is sensedby a pair of biopotential sensing electrodes 5 (although, other sensingmechanisms may be used). The EKG sensor ensures that the power supplyoperates the pump motor only in diastole (relaxation). Typically, EKGsignals occupy about a 100 Hz bandwidth, and have a dynamic range ofamplitude varying between 20 μV-5 mV. In one aspect, these EKG signalsare relayed to the power supply 1 either via a wire, as commonly done intypical pacemakers, or communicated wirelessly with the help of adigital control unit 6. Drug infusion can start 80 milliseconds after a2.5 mV biopotential is sensed (i.e., QRS deflection) and stops with thenext biopotential sensing (i.e., next QRS deflection). According to oneembodiment, the sensing electrodes 5 and the associated system are basedon the design proposed in the following technical publication: “AWireless Batteryless In Vivo EKG and Body Temperature SensingMicrosystem with Adaptive RF Powering For Genetically Engineered MiceMonitoring” by Nattapon Chaimanonari and Darrin J. Young, incorporatedby reference herein. The sensing electrodes 5 may include virtually anysensing mechanism as will occur to one of ordinary skill in the art.

Digital Control Unit

In one embodiment, a pair of biopotential sensing electrodes 5 isconnected to a digital control unit 6. Digital control unit 6 furtherincludes an 8 bit analog to digital (A/D) converter, a detector forsensing RF power, and a parallel to serial converter. As will beunderstood, EKG or hemodynamic data (dp/dt) is digitized to 8 bits.Furthermore, in one aspect, the digitization process (or, in general,the digital control unit 6) clamps a positive dp/dt value to output one(‘1’) if the positive dp/dt value exceeds a predetermined threshold.Similarly, the digitization process clamps a negative dp/dt value tooutput one (T) if the negative dp/dt value is less than a predeterminedthreshold. Alternately, a positive dp/dt value is clamped to output zero(‘0’) if the positive dp/dt value is less than the predeterminedthreshold. Similarly, a negative dp/dt value is clamped to output zero(‘0’) if the negative dp/dt value exceeds the predetermined threshold.The performance of a patient's heart, in such situations, is given bythe ratio of output one (‘1’) and output zero (‘0’).

Subsequently, the digitized data is appended to a one bit RF power leveldata; the resulting data is converted into a serial data stream using aparallel to serial converter (in conjunction with a multiplexer, andfinally transmitted to the RF transmitter 7. Details of a digitalcontrol unit are described in the article: “A Wireless Batteryless InVivo EKG and Body Temperature Sensing Microsystem with Adaptive RFPowering For Genetically Engineered Mice Monitoring,” by NattaponChaimanonari and Darrin J Young, incorporated by reference herein.Therefore, further details are not described herein. As will beappreciated, in alternate embodiments, a digital control unit includes amicroprocessor, or any other combination of electrical componentsproviding the various functionalities described above.

RF Transmitter

The physiological data comprising a patient's vital signs such as rightventricle pressure, EKG signals, etc. are sent to an RF transmitter 7,and then transmitted wirelessly from internal RF transmitter 7 to theexternal RF receiver 9. In one embodiment, the RF transmitter 7 can be aFrequent Shift Keying (FSK) transmitter. FSK is a frequency modulationscheme in which digital information is transmitted through discretefrequency changes of a carrier signal. As will be understood andappreciated, however, embodiments of the disclosed device are notlimited to the specific RF transmitter described.

Adaptive RF Powering System

In one embodiment, an external adaptive RF powering system is coupledwirelessly to the digital control unit to regulate the voltage supplyfor the implantable device.

RF Receiver

The RF data received at the RF receiver 9 can be stored in a digitalcomputer for future analysis and can also be used to determine infusionrate of the drug. In one embodiment, the RF receiver 9 can be a FrequentShift Keying (FSK) receiver. As will be understood and appreciated,however, embodiments of the disclosed device are not limited to thespecific RF receiver described. The data received at the RF receiver 9can be stored in a digital computer for future analysis and can also beused to determine the infusion rate of the applicable drug. As will beunderstood, automatic adjustment of the infusion rate is alsoprogrammable through the RF transmitter 7, RF receiver 9 and powersupply 1. Initially, however, dose adjustment should be done manuallyand externally by the clinician reviewing stored data, although this isnot technically required for operation of the disclosed device.

External Adjustment Mechanism

An external adjustment mechanism 10 allows the external unit to be offlexible design. In one embodiment, the external adjustment mechanism 10is designed such that the entire external unit of the implantable druginfusion system could be assembled into a single handheld unit(comparable to the size of state-of-the-art smartphones of today), thatcan further fit inside a case or can be worn on a belt. The handheldunit can include a personal digital assistant (PDA), smartphone, tablet,or other portable computing device. Therefore, it will be understood andappreciated that the disclosed drug infusion system provides thebenefits of being lightweight and portable.

The corresponding structures, materials, acts, and equivalents of allmeans plus function elements in any claims below are intended to includeany structure, material, or acts for performing the function incombination with other claim elements as specifically claimed.

Those skilled in the art will appreciate that many modifications to theexemplary embodiments are possible without departing from the scope ofthe present invention. In addition, it is possible to use some of thefeatures of the embodiments disclosed without the corresponding use ofthe other features. Accordingly, the foregoing description of theexemplary embodiments is provided for the purpose of illustrating theprinciples of the invention, and not in limitation thereof, since thescope of the invention is defined solely by the appended claims.

What is claimed:
 1. A system for physiological monitoring and regulationof a drug infusion device, comprising: an internal compact unit that isimplantable in a patient having a pulmonary disorder, the internal unitencasing a power supply, a fluid reservoir, a motor pump, a digitalcontrol unit, and a radio frequency transmitter; an infusion catheterconnected to the fluid reservoir and motor pump for automaticallyinfusing a drug into a right ventricle of the patient during a diastolephase of a cardiac cycle; and an external unit for monitoring andstoring of a plurality of physiological parameters of the patient andfor making adjustments to a drug infusion rate.
 2. The system forphysiological monitoring and regulation of claim 1 wherein the infusioncatheter comprises a hemodynamic pressure sensor and a biopotentialsensor.
 3. The system for physiological monitoring and regulation ofclaim 1 wherein the external unit comprises an RF receiver, an adaptiveRF powering system, and an adjustment component.
 4. The system forphysiological monitoring and regulation of claim 1 wherein the fluidreservoir comprises a subcutaneous chamber for storing the drug to beautomatically infused into the right ventricle.
 5. The system forphysiological monitoring and regulation of claim 4 wherein the motorpump is connected to the power supply and pumps the drug from the fluidreservoir chamber to the infusion catheter wherein the drug flow rate isregulated by an output from the power supply to the fluid reservoirchamber.
 6. The system for physiological monitoring and regulation ofclaim 1 wherein the internal compact unit has a shape that is eithercircular or elliptical and is approximately the same size as a pacemakerpulse generator.
 7. The system for physiological monitoring andregulation of claim 1 wherein the infusion catheter comprises a radiallydense helical structure made of a polyurethane material and having asupporting steel frame.
 8. The system for physiological monitoring andregulation of claim 1 wherein the infusion catheter is anchored to awall of the patient's right ventricle.
 9. The system for physiologicalmonitoring and regulation of claim 2 wherein the hemodynamic pressuresensor is located at a tip of the catheter and measures a relativechange in right ventricle pressure over time which is indicative of acondition of a pulmonary artery.
 10. The system for physiologicalmonitoring and regulation of claim 9 wherein the drug infusion rate canbe automatically increased if the relative change in pressure exceeds apredetermined threshold associated with pulmonary hypertension.
 11. Thesystem for physiological monitoring and regulation of claim 2 whereinthe biopotential sensor comprises a biopotential sensing electrodelocated at a tip of the catheter for sensing an electrocardiogramsignal.
 12. The system for physiological monitoring and regulation ofclaim 11 wherein the biopotential sensor and the pressure sensor areconnected to the digital control unit which digitizes a plurality ofphysiological signals received from these sensors and sends thedigitized physiological signals to the radio frequency transmitter. 13.The system for physiological monitoring and regulation of claim 12wherein the radio frequency transmitter transmits the digitizedphysiological signals wirelessly to the radio frequency receiver. 14.The system for physiological monitoring and regulation of claim 13wherein the radio frequency receiver comprises a frequent shift keyingreceiver and is connected to the external adjustment component.
 15. Thesystem for physiological monitoring and regulation of claim 13 whereinthe adjustment component comprises a handheld electronic device.
 16. Aninfusion catheter for delivery of a drug into a patient having apulmonary disorder, comprising: a radially dense helical structure madeof a polyurethane material and having a supporting steel frame to ensureunidirectional flow and prevent clotting within the catheter; ahemodynamic pressure sensor mounted on a tip of the catheter formeasuring a relative change in hemodynamic pressure over time; and abiopotential sensor including a biopotential sensing electrode mountedon a tip of the catheter for sensing an electrocardiogram signal of thepatient; wherein the infusion catheter is connected to a fluid reservoirand a motor pump in an implantable device and automatically infuses adrug into a right ventricle of the patient during a diastole phase of acardiac cycle at a rate dependent on the measured change in hemodynamicpressure.
 17. The infusion catheter of claim 16 wherein the helicalstructure acts as a fluid reservoir during a systole phase of thecardiac cycle.
 18. A method for hemodynamic monitoring of a patientdiagnosed with pulmonary hypertension and infusing a therapeutic drug byan implantable drug infusion device, comprising: monitoring the relativechange in hemodynamic pressure in a patient's right ventricle over timeby a pressure sensor mounted on a tip of an infusion catheter in theimplantable device; sensing an electrocardiogram signal of the patientby a biopotential sensor including a biopotential sensing electrodemounted on a tip of the infusion catheter; infusing the therapeutic druginto the right ventricle during a diastole phase of a cardiac cycle at arate dependent on the monitored relative change in hemodynamic pressure,the drug being pumped from a fluid reservoir in the implantable devicethrough the infusion catheter into the patient's right ventricle throughan infusion port.
 19. The method for hemodynamic monitoring of claim 18further comprising automatically increasing the drug infusion rate ifthe monitored relative change in pressure exceeds a predeterminedthreshold.
 20. The method for hemodynamic monitoring of claim 18 furthercomprising digitizing a plurality of physiological signals received fromthe biopotential sensor and pressure sensor and sending the digitizedsignals to a radio frequency transmitter for wireless transmission to anexternal unit for making adjustments to the drug infusion rate by aportable electronic device.
 21. The method for hemodynamic monitoring ofclaim 18 wherein the drug infusion rate is regulated by an output signalfrom a power supply in the implantable device to a fluid reservoirchamber in the implantable device.
 22. The method for hemodynamicmonitoring of claim 18 wherein the electrocardiogram signal is used todetermine when to start and stop infusion of the therapeutic drug. 23.The method for hemodynamic monitoring of claim 18 further comprisingstopping infusion of the therapeutic drug if the monitored relativechange in hemodynamic pressure falls below a threshold value.
 24. Themethod for hemodynamic monitoring of claim 1 wherein the drug infusiondevice is implanted inside a pocket positioned under a collar bone andconnected to the right ventricle using the infusion catheter.